Epidemiologic data strongly suggest that acquired immune deficiency syndrome (AIDS) is caused by an infectious agent transmitted by intimate contact or blood products. Though the disease is manifested by opportunistic infections, predominantly Pneumocystis carcinii pneumonia and Kaposi's sarcoma, the underlying disorder affects the patient's cell-mediated immunity with absolute lymphopenia and reduced helper T-lymphocyte (OKT4.sup.+) subpopulation(s). Moreover, before a complete clinical manifestation of the disease occurs, its prodrome, pre-AIDS, is frequently characterized by unexplained chronical lymphadenopathy and/or leukopenia involving a helper T-cell subset. This leads to the severe immune deficiency of the patient, suggesting that a specific subset of T-cells is the primary taret for an infectious agent. Although patients with AIDS or pre-AIDS are often chronically infected with cytomegalovirus or hepatitis B virus, for various reasons these appear to be opportunistic or coincidental infections apparently not linked to the immunological response deficiency. The virus which causes AIDS, HTLV-III, is in the family of human T-cell lymphotropic retroviruses (HTLV) which comprises two major well characterized subgroups of human retroviruses, called human T-cell leukemia/lymphoma viruses, HTLV-I and HTLV-II.
Human T-lymphotropic virus type III (HTLV-III)/-lymphadenopathy-associated virus (LAV) is a newly discovered lymphotropic retrovirus which is cytopathic for helper/inducer T-cells in vitro. This virus is the etiologic agent of the acquired immunodeficiency syndrome (AIDS) and related diseases. Although a number of anti-viral agents are now being considered for the experimental therapy of AIDS, to date no therapy has been shown to cure HTLV-III/LAV infection or restore the underlying immunodeficiency. Moreover, the chronicity of infection and the propensity of the virus to infect the brain make it necessary to explore new classes of drugs which have the potential for oral administration and penetration across the blood-brain barrier.
The search for therapeutic reagents capable of inhibiting or inactivating HTLV-III/LAV has received a much publicized concerted effort on the part of scientists and doctors to find a cure for AIDS. The traditional in vitro screening systems involve the use of H9, CEM, MT-2, and/or MT-4 cells--clones of HTLV-III developed by Gallo and co-workers. These clones are described in Popovic, et al., Science, Vol. 224, p. 497 (1984) and Sarngadharan, et al., Science, Vol. 224, p. 506 (1984).
These older clones, however, are partially resistant to the cytopathic effects of HTLV-III. Because of this, use of H9, CEM, MT-2, or MT-4 cells requires an immunofluorescent assay or reversetranscriptase assay to monitor the effects of a putative drug or biologic that is being tested for an inhibitory effect against the virus.
On the other hand, the present invention--incorporating the newly developed cell line--is rapid, is useful for direct visual inspection (pellet size of target cell cultures) with confirmatory counts in a simple hemocytometer, and is highly sensitive. Furthermore, the present invention is readily adaptable for mass screening (hundreds of compounds at a time) and requires very little expenditure of labor and no unusual training on the part of the test operator. For additional comparisons of ATH8 to the other known clones, see Example 5.